Hydroplane



April 5, 1932. g, SHAW 1,852,680

HYDROPLANE Fild June 27, 1950 5 Sheets-Sheet 1 In fen [on Char/es Shaw.

April 5, 1932. c. SHAW 1,852,680

HYDROPLANE Filed'June 27, 1930 3 Sheets-Sheet 2 April 5, 1932. c SHAW 1,852,680

HYDROPLANE Filed June 27, 1930 3 Sheets-Sheet 3 In Mentor. Char/es Ska.

Patented Apr. 5, 1932 UNITED STATES CHARLES SHAW, OF HUNTSVILLE, ONTARIO, CANADA HYDROILAN E Application filed June 27,

The principal objects of this invention are to enhance the planing proclivity of pleasure and speed boats, so that greater speeds and smoother and safer riding and turning may be obtained, and to lessen the power required in attaining these results.

One of the principal features of the invention consists in the novel construction and arrangement of hydrofoils directly beneath the boat hull, whereby the dead weight of the craft is relieved, either partially or wholly from contact with the water, thus ensuring smoothness of movement; while the centre of gravity is maintained at the lowest possible point at all speeds and the stability and attractive appearance of the craft is retained.

A further and very important feature of the invention consists in the provision of means for effectively preventing cavitation 241 around the the means for supporting the bull in its elevated position whereby the maximum lift to drag ratio of the supporting means will be ensured.

The present day craft of pleasure and of boat capable of remarkably high speeds and the maximum speeds with the step or other surface planing types of boat have been obtained mostly through the reduction of weight per horsepower in the engines used, but the greater speed developed has rendered the difliculties of hull construction, to provide smooth and comfortable riding qualities, practically insurmountable on account of the a; tremendous shocks encountered in the impact of the water against the hull.

Other forces resultant from the great speed of a large body such as the hullof the boat over the water surface have also presented great obstacles to further development, the chief of these being lack of control at high speeds.

Various types of craft have been devised in an efiort- ,to overcome the difliculties encountered through the use of submerged hydrofoils to relieve the dead weight of the craft from contact with the water and some have been successful in lifting the entire body of the craft clear of the Water but though high speeds have been attained such strucspeed boat construction has developed types 1930. Serial No. 464,255.

ted to the suction surface of the foil breaking 7 water and also to the suction surface of the fo1l immediately therebelow. The cavitation of air thus created around the foil sets almost completely destroys the suction lift the first one or two foils at or below the surface of the water, which so seriously reduces the lift to drag ratio that much of the advantage expected from increased speed is lost.

This condition will be more fully appreciated from the fact that the suction on the top surface of a cambered hydrofoil is' exactly similar to that of an aeroplane, and that, depending on the speed, from 20% to of the lift is created by the partial vacuum over the upper surface of the plane or foil. Under these conditions it will be appreciated that at top speed the hydrofoils are reduced to the actual lifting value of the pressure surfaces, which may easily be in less favorable proportion than is found in well-designed surface planing craft.

It will also be appreciated that the use of the foil sets at high speeds raises the centre of gravity of the craft an abnormal distance above the water surface and this necessitates the spreading of the sets laterally each side of the craft to stabilize it against capsizing when turning. This spreading of the sets renders it impossible to properly bank the boat in turning sharply at high speeds in order that a comfortable feeling will be experienced.

A further and very important objection to the use of the foil sets is the danger to the craft in fouling obstructions which may be on or below the surface and also that the craft has a freak appearance and requires most extraordinary mooring or docking facilities.

The present invention proposes to control the lift of the boat bull to relieve the dead weight from impact against the water by means of a single hydrofoil and the construction and arrangement of such foil is capable of great variation.

In the use of hydrofoils it will be obvious that in addition to the foils themselves breaking water and causing cavitation the struts connecting the hull with the foils, in cutting through the water, create a cavity which leads to the foil surface and air trailing down the edge of the strut will form a cavitation bubble on the upper surface of the foil which destroys thesuction lift. I

The present invention consists in providing means for preventing the flow of air to suction lifting-surfaces and arranging suitable baffles to close spaces which may be found back of the struts or other supports and along the top surface by their movement through the water so that they will be sealed against any inflow of air.

In the accompanying diagrammatic drawigure 1 is a side elevational view of a boat equipped with a hydrofoil showlng an arrangement of baflles to prevent cavitation.

Figure 2 is a plan of the baflie arrangement shown in Figure 1.

Figure 3 is an enlarged detailed side elevational sectional view of the foil and bafiles.

Figure 4 is a plan section of a portion of a foil and strut shown in Figure 3.

Figure 5 is a plan section of a portion of a foil and strut not protected with baflies, showing the cavitation formation on the upper foil surface caused by the cavitation behind the strut.

Figure 6 is a plan sectional diagram of a modified arrangement of strut baflles.

Figure 7 is a front elevational view of a boat showing a hydrofoil equipped with av plurality of baflles and the tips of the foil breaking water.

Figure 8 is a side elevational view of the foil shown in Figure 7 Figure 9 is a plan view of the hydrofoil as shown in Figure 7 illustrating the use of the top baflles in preventing cavitation when the foil breaks water at the ends.

Figure 10 is a plan view of a hydrofoil not equipped with baflies illustrating the cavitation effect when breaking water at the ends.

Figure 11 is a front elevational view of a boat showing an arrangement of non-cavitating hydrofoil.

Figure 12 is a side elevational view of a foil showing a modified form of baflie for directing a water baflie to prevent cavitation.

Figure 13 is a front elevational View of the bafile shown in Figure 9.

Figure 14 is a front elevation showing the relation of the hydrofoil and the direction of forces in a banking movement.

In the application of the invention herein illustrated, Figure 1 shows a side elevational view of an ordinary form of step hydroplane.

Attached to the boat bottom on the planes forward of the step 1 by means of the strut 2 is a hydrofoil 3.

It is preferable that the hydrofoil be formed with dihedral angles as illustrated in Figure 5, and the struts 2 are preferably arranged adjacent to the outward ends of the foil though a central strut may be used if desired, as illustrated in Figure 2.

The body of the foil will be formed of such design and dimensions as will be most suitable to the craft to which it is to be applied, but is quite similar to the design of an aeroplane wing.

The struts 2 will be sturdy and of considerable cross sectional area but will be stream lined to offer the least resistance to the flow of water therepast.

It is a well known fact that it is not possible to construct a foil or struts of such dimensions as to support a heavy body that will not cause a certain amount of cavitation in cutting through the water at speed if air has access to the top of the strut or foil.

The stream line flow of water over the cambered surface of the foil creates a suction lift which at high speed has a greater load supporting value than that of the pressure surface and this is sustained even though the water may not closely follow such surface but in the event of air being admitted to the suction surface through the tips of the foil breaking the surface or through the drag of supporting struts through the water, the suction lift is destroyed and the value of the foil is reduced to that of a surface plane and there is no advantage obtained over a well designed surface plane.

In order to overcome this difiiculty I propose the arrangement of baflie plates 4 upon the struts intermediate of their height at such a distance above the top surface of the foil and at such a slant as to not interfere pitlh the smooth flow of the water over the The baflle' 4 extends outwardly sidewise from the strut to prevent cavitation at the sides when side slip occurs. The bafile extends rearwardly of the strut to trail a sufficient distance to ensure the prevention of a cavity being opened up behind the strut and below the baffle through the passage of the strut through the water.

The arrangement of this baflle will, while the baflie remains below the water surface prevent the flow of air down the trailing edge of the strut to the top or suction surface of the foil and cavitation on such surface from that source will be prevented.

In the forward movement of the foil through the water when a part thereof breaks surface of the foil and to trail beyond the rear edge of the foil a sufiicient distance to close the cavity formed by the wash of water over the top side of the foil.

This arrangement of a ba-flie extending 'above the upper foil surface prevents air following the surface of the foil and the suction effect of the upper surface of the foil which with the baflie remains submerged will 'be maintained.

Figures 2 and 3 of the drawings illustrate the arrangement of these bafiles 4 and 5 very clearly and Figure 4 diagrammatically illusfrates the manner in which the trailing space is formed behind the strut and forms a cavitation bubble on the surface of the foil and such cavitation bubble once formed will be maintained as long as the boat continues. to move at such a speed as will form a cavity behind the strut.

Bafiies may be arranged on either side of a strut in such a position as to maintain surface contact of the stream line surface of the strut with the water. This modification is illustrated in Figure 6 in which the vertical bafile plates 2 are arranged at either side of the strut 2 and converge slightlytoward the rear so as to direct the slip stream into close contact with the back surfaces of the strut.

It may be found desirable in certain designs of foils such as those covering a wide range of speed and lift, to provide baffles at intervals along the upper side of the foil structure so that if speed attained by'the craft is sufli-,

cient to raise the foil tips clear of the water, the maximum suction effect of the'upper side of the foil remaining submerged will be maintained by the arrangement of the bafiies 6 These trail beyond the rear edge of the foil to close the arched flow cavity against the ingress of air to the submerged foil surfaces.

Figure 9 is a plan view diagrammatically illustrating the manner in which the inward flow of air under the stream line of fiow of the water is interrupted by the trailing baflie.

tain the efficiency of the portion of the foil remaining submerged.

The diagram in Figure 10 illustrates the effect of the free access of air to the upper. surface of the foil when the tips thereof break water. The stream line flow of water forms the cavities 8 and an flows inward and makes an almost complete break in the suction lift.

It will be readily appreciated that the design of the baflles and the design of the hydrofoils may be altered very materially while still functioning in the same practical manner. J

Figures 12 and 13 illustrate a modification of baflie in which the strut 10 is shown formed with a forwardly and rearwardly extending web portion 11.

The horizontal bafiie 12 is formed with convergent under side planes 13 which slope outwardly and backwardly from the upper surface of the coil and the front edge of the strut.

This form of bafiie parting the water will project a spray sheet as the water flows thereunder which will form an effective trailing bafile to prevent the inflow of air to the upper surface of the foil past the strut. Such a construction will enable the reduction of area offering lateral resistance in turning'to the minimum.

The arrangement of the foil in a design similar to that shown in Figure 7 presents dihedral angles when the boat is caused to swerve in its course to make a turn by the action of the rudder and naturally causes the commencement of a bank.

The true angle of effectiveness of the hydrofoil is measured in the plane of the flow of the water past the boat and as aboat tilts into a bank in turning, the lower wing of the foil, or the side on the direction of turn, is lessened and the angle of incidence on the other wing is increased over the normal angle of incidence due to the side slip. This condition is very fully defined in Airplane Design, Aerodynamics, by E. P. Warner, 1927, pages 409-412.

It is of course very important in the bank of the boat to retain the centre of gravity as low as possible and the use of the single dihedral foil accomplishes this in a remarkable manner.

It will be seen on reference to the diagram in Figure 14 that as the boat swings into a bank the outer wing will be tipped so as to offer much greater resistance to the side movement ofthe boat than that of the other side which is to effect a reduction of lift or to actually create a downward pull and the result is that the applied forces are such that the foil is drawn or forced by the weight of the boat into the water so that the diagonal force of the outer wing effects the turning of the boat.

The functioning of the dihedral foil arranged directly beneath the boat in effecting turns is very positive and produces a desirably uniform result at all planin speeds in View of the fact that the centri ugal force increases as the square of the speed and the reaction from the foil also increases in the same ratio, the angle of turn regulating as the radius of turn is also in proportion to the increase of centrifugalforce from this variable.

When foils of the ladder type are used it is usual that they are supported by struts from the boat hull at an angle dihedral to the water line. At high speeds the boat is raised a very considerable distance above the water and the result is the raising of the centre of gravity which necessitates the spreading of the foil sets on either side of the boat to prevent capsizing. This spreading of the foils makes it impossible to bank the boat and the feeling on a sharp turn is one of insecurity. Further, the protruding foil sets are always dangerous in respect to encountering obstacles or other craft. Single hydrofoils such as described may be designed to very materially reduce the surface friction and water contact from the present types of hydroplanes which will function to relieve the dead weight of the boat at considerably low speeds and may be depended upon to lift the boat substantially clear of the water, or entirely so.

This result can no doubt be accomplished with very much less foil area than with the type of hydrofoil arrangement known as the set type on account of the maintenance of the maximum of the suction lift effected upon the foils and the reduction in depth with a consequent lowering of the centre of gravity and drag of the struts.

It will be understood that not only can the areas of the hydrofoils be altered to a desirable extent but the actual design of the hydrofoil, both in respect to its cross section and its supports and its dihedral angularity and sweepback may be varied in an almost limitless scope to accommodate the principles involved to different types, weights and speeds of boats and further, such hydrofoils may be placed in various positions on the underside of the hull without departing from the principal feature of the invention.

The design of foil with a marked sweepback, as illustrated in Figure 2, may be developed to provide a most effective foil effect and such design enables the balancing of force lines to the centre of gravity in turning.

It will be noted on reference-to Figure 1 of the drawings that the horizontal baffles on the various supports of the hydrofoil and propeller shaft, etc., are arranged below the water line and also below the line of travel of air which may be forced beneath the hull so that no air will be directed below the cavitation baflles so that it can reach the planing surfaces below the'water surfaces to destroy or materially reduce their suction lift.

What I claim as my invention is:

1. The combination with a boat hull, of a hydrofoil spaced below said hull, and means spaced below the hull bottom and extending rearwardly of said foil for preventing cavitation around said foil.

2. The combination with a boat hull, of a hydrofoil spaced from the hull, means for supporting said foil from said hull, and means for sealing the cavity formed in the wake of said supporting means to prevent access of air to the upper surface of the foil.

3. The combination with a boat hull, means of support extending from the hull, a hydrofoil spaced from the hull and rigidly mounted on said supporting means, and bafiies arranged transversely of said supporting means and trailing back of said support to prevent the flow of air to the upper foil surfaces.

4. The combination with a boat hull, supporting means extending from the hull, a hydrofoil spaced from the hull and rigidly mounted on said support, and baffles arranged on said support intermediate of the length thereof and extending laterally and rearwardly therefrom.

5. The combination with a boat hull, supporting means extending from the hull, a hydrofoil spaced from the hull and rigidly mounted on said supports and presenting upwardly and outwardly diverging foil sections, means for interrupting the flow of air down said supports, and a plurality of spaced baffles extending upwardly from the upper surface of each of said foil sections and trailing rearwardly of the latter whereby a progressive seal is formed to limit the flow of air along the foil surfaces in accordance with the depth to which said foils are submerged.

6. The combination with a boat hull, supporting means extending from the hull, a hydrofoil spaced from the hull and rigidly mounted on said support, and baffles extending upwardly from the upper surface of said hydrofoil and trailing beyond the rear edge of said foil.

7. The combination with a boat hull, supporting means extending from the hull, a hydrofoil spaced from the hull and rigidly mounted on said support, bafiies extending transversely from said supports and trailing behind same, and bafiies extending rearwardly from said support between the aforesaid baflles and the foil.

8. The combination with a boat hull, supporting means extending from the hull. a hydrofoil spaced from the hull and rigidly mounted on said support, and a plurality of baflles separate from said support extending from front to rear of said foil and disposed in angular relation thereto whereby access of air to the upper foil surfaces is restricted.

9. The combination with a boat hull, of a hydrofoil spaced below the boat hull and extending outwardly from the centre at dihedral angles and spaced supports extending hedral angles, and means from the respective angular sections of said foil and connected to said hull and presenting small resistance to side slip of the hull in turning, whereby a pronounced banking ingu ince on the hull is produced by said hydro- 10. The combination with a boat hull, of a hydrofoil arranged beneath and spaced from the boat hull and extending upwardly and outwardly at dihedral angles and having anti-cavitation baflles extending upwardly therefrom, said bafiles being arranged transversely of said hydrofoil and trailin rearwardly thereof to restrictthe access 0% air to the upper foil surfaces.

11. The combination with a boat hull, of a strut extending downwardly from the hull having a transverse baffle arranged intermediate of its length flared outwardly and rearwardly on its underside and adapted to throw a baflling sheet of water to prevent cavitation, and a hydrofoil attached to said strut below said baflle.

12. The combination with a boat hull, of a hydrofoil spaced from the hull, means for supporting said foil from said hull, and means for directing a sealing flow of water rearwardly of said supportin means to close the cavity formed in the wa e of the latter whereby access of air to the upper foi l surfaces is restricted.

13. The combination with a boat hull, of a hydrofoil spaced below the boat hull and extending outwardly from the centre at dirigidly connected to said hull and supporting said hydrofoil in fixed relation to said hull, said supporting means being shaped to present a comparatively small resistance to side slip of the hull in turning, whereby the action of the water on the respective angular portions of the hydrofoil will impart a pronounced bank to the hull.

CHARLES SHA'VV. 

